Top Zika Vaccine Candidate Moves Closer to Field Testing

MONDAY, Oct. 3, 2016 (HealthDay News) -- The leading Zika vaccine candidate should be ready for field testing should new outbreaks occur next year, U.S. health officials announced Monday.

Over the weekend, researchers finished recruitment of the 80 volunteers needed for phase 1 trials of a DNA vaccine to protect against Zika, said Dr. Anthony Fauci, director of the U.S. National Institute for Allergy and Infectious Diseases (NIAID). In a Phase 1 trial, a drug or vaccine is tested in a small group, largely for safety.

"This trial is right on target -- in fact, a bit ahead of time," Fauci said. "It is projected we will have enough information to determine safety and whether it induces the kind of response we predict would be protective."

The DNA vaccine is on track for phase 2 field testing by January, if it proves safe and Zika outbreaks begin with the start of summer in South America, Fauci said. Phase 2 trials test the effectiveness of a drug or vaccine in larger numbers of people.

Researchers hope to include between 2,400 and 5,000 people in the phase 2 trials. The trials will be conducted in at least 15 locations where active Zika transmission is occurring. That could include the United States if an outbreak of Zika occurs next summer, Fauci said.

The DNA vaccine is the furthest along of nine candidate Zika vaccines, the health officials said Monday.

Developed by NIAID's Vaccine Research Center, the DNA vaccine contains a fragment of Zika's genetic makeup that has been recreated synthetically in the laboratory. The vaccine is intended to produce small virus-like particles similar enough to Zika to prompt an immune response that would shield the body against future infection from the virus.

Last month, researchers reported in the journal Science that a two-dose regimen of the DNA vaccine successfully protected 17 of 18 monkeys from Zika infection.

Zika is the first mosquito-borne virus known to cause terrible birth defects, most of them brain-related.

The most common defect is microcephaly, in which a child is born with an abnormally small brain and skull. Thousands of babies have been born with Zika-linked microcephaly, most of them in Brazil, since an outbreak began in South America in April 2015.

However, researchers have detailed so many different brain defects linked to Zika that they have now proposed using the term "congenital Zika syndrome" when reporting on future cases.

Zika infections have been occurring in south Florida since summer, with 124 cases reported as of Sept. 30, according to the U.S. Centers for Disease Control and Prevention. While 97 of those cases involved pregnant women, there have been no reports of microcephaly in the state.

Congress last week authorized $1.1 billion to fight Zika, and Fauci said the money will allow his researchers to "proceed in a smooth fashion" with the phase 2 DNA vaccine trial. For example, they will be able to produce enough doses in advance of the next Zika outbreak, he said.

Officials said the new funding also will be used to pay for:

Better research coordination between universities and public health departments,

Emergency teams to react to Zika outbreaks,

Expanded mosquito-control efforts,

Research into long-term effects of Zika infection, particularly in children with no obvious birth defects,

Preparations for major vaccine manufacturing, once a vaccine has been approved.